Physical and Chemical Properties and Changes. Matter: anything that has mass and takes up space...

Physical and Chemical Properties and Changes

• Matter: anything that has mass and takes up space– Mass – the amount of matter in something– Volume – the amount of space something

occupies

• Which of the following is matter?– A car?– A box?– You?

Reviewing MATTER

What is a property?

• Property: a characteristic of a substance that can be observed

Physical Property

Physical property: a property that can be observed without changing the identity of the substance.

Examples:

• luster

• malleability: the ability to be hammered into a thin sheet

• ductility: the ability to be stretched into a wire

• melting point

• boiling point

• density

• solubility

• specific heat

Special Physical Properties

• Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressure

• Boiling point: the temperature at which a substance changes from a liquid to a gas at a given pressure

water = 100oC

Chemical Properties

• Chemical property: a property that can only be observed by changing the identity of the substance

Examples:

•flammability

•ability to rust

•reactivity with vinegar

Matter can be changed two ways

• Physically Physical reaction

Physical change

• Chemically Chemical reaction

Chemical change

Physical Changes

• Do NOT CHANGE THE TYPE OF MATTER –Nothing new or different is

formed• Could be a change in:

–Size, Change in state, Color, Shape

Examples of Physical Changes

• Boiling, Freezing, Dissolving, Breaking

• Making a mixture 2 or more types of matter (substances) mixed together – Not in specific amounts– Can be separated physically

Chemical Changes• The composition of the

substance changes.• The substances

present at the beginning of the change are not present at the end; new substances are formed. The change cannot be “undone.”

Picture from www.chem4kids.com

Evidence of a chemical reaction

–Formation of gas –Formation of precipitate –Change in color –Change in energy

Types of Reactions

• Endothermic Absorbs heat energy (The substance gets warm, while the environment gets cold)

• Exothermic Releases heat energy (The substance gets cooler, while the environment gets warmer)

Chemical Changes• Atoms are re-arranged, NOT created or

destroyed

Law of Conservation of Matter

• Matter is conserved type of atoms does not change – Nothing is created or destroyed